1. Field of the Invention
The present invention relates to an image reading unit that reads an original image, for example, a scanner, a copying machine, a facsimile machine, or the like and an image reading apparatus having the image reading unit.
2. Related Background Art
Up to now, various image reading apparatuses such as an image scanner which reads the image information of an original and forms digital image information have been put into practical use.
In recent years, as the image reading apparatus of this type, an all-in-one optical system unit that can simplify the structure as the entire apparatus and complete an optical adjustment only within the unit is used a lot, although the image reading unit (carriage) per se becomes large.
An example of the image reading apparatus that reads an original by using the image reading unit (carriage) which is the all-in-one optical system unit will be described with reference to FIGS. 16 to 18. FIG. 18 is a schematic cross-sectional view showing the image reading apparatus.
In order to read the image information, an original P is set on an original glass stand 91 and the original P is set at a regular position with its image side facing inward of an apparatus case, that is, facing downward, and an original pressure plate 92 pushes a back side of the original P from the upper side so as not to displace the original P on the original glass stand 91.
An image reading unit (carriage) 101 having photoelectric conversion means (an image sensor) which is disposed opposite to the original P with the original glass stand 91 interposed therebetween is so structured as to read image information for one straight line (image information obtained by main scanning for one line), and in order to read the image information of the original P, the image reading unit 101 is moved in parallel in a sub-scanning direction from a leading end of the original P to a trailing end thereof by a drive motor (not shown). With the above structure, the image reading unit 101 can read a two-dimensional plane image of the original image.
FIG. 17 shows an enlarged cross-sectional view showing the image reading unit (carriage) 101, and FIG. 16 shows a basic structural diagram of the image reading unit (carriage) (a lamp and so on are omitted).
A lamp 3 that serves as a light source, a reflecting mirror (reflector) 4 disposed on a back side of the lamp 3 and a reflecting mirror (reflector) 5 disposed in the vicinity of the lamp 3 lightens a required portion of the original P in a linear manner in a main scanning direction.
The original glass stand 91 on which the original P is set is omitted from the figure.
The light reflected from the image surface of the original P is guided to a lens unit 11 that images an optical image through a first mirror 6, a second mirror 7, a third mirror 8, a fourth mirror 9 and a fifth mirror 10 which are optical mirrors, and the original image is imaged on an image sensor 2 that serves as the photoelectric conversion means.
The image sensor 2 is so designed as to conduct a photoelectric conversion to form the image information.
Then, after the data for one line is processed, the image reading unit (carriage) 101 is moved in a sub-scanning direction by only one line, to prepare the image information in the above manner, and this operation is repeated.
Also, there is a case in which the illuminance of the light from the light source 3 toward the original P becomes uneven in the main scanning direction or the characteristics of each pixel of the image sensor 2 are different from each other. As a result, any discrepancies in producing the image information becomes wide.
In order to correct the discrepancies, shading correction of white and black is required, and a white reference plate for white shading and a black reference plate for black shading are disposed at positions where the image reading unit (carriage) 101 can shade on the extension line of the sub-scanning direction and out of an original image reading range, respectively.
However, the above-described conventional art suffers from the following problems.
As is apparent from the above description, since the optical adjustment of the image reading unit (carriage) is conducted only within the unit, an image sensor with a higher resolution image can be used.
In order to sufficiently exhibit the efficiency of the image sensor with the high-resolution image, the performance of the lens unit which is another important part of the image sensor must be suited for the image sensor for the high resolution image.
Therefore, there arises such a problem that if the technical precision of the optical adjustment is not very high, the capacity of the high resolution image sensor and the high performance lens unit cannot be effected.
Since the image sensor is normally fixed to the carriage by soldering or the like so as to be disposed within a free space, even if an assembling adjustment jig with a high precision or the like is used in order to forcedly enhance the technical precision of the optical adjustment, slight displacement may occur at the time of finally fixing the image sensor by soldering or the assembling property is remarkably deteriorated.
Also, in the case where the optical adjustment failure occurs, the original image reading fails or it takes too much time to recycle the image reading unit.
The present invention has been made to solve the above problem with the conventional art, and therefore an object of the present invention is to provide an image reading unit and an image reading apparatus which improves the adhesion when a first unit having photoelectric conversion means is adhered to a second unit with an adhesive.
Another object of the present invention will become by reading the following detailed description.